1. Field of the Invention
The present invention relates to a battery charging apparatus, and more particularly, to a battery charging apparatus that commonly uses a power conversion structure in an on board charger (OBC) so that an auxiliary battery is also charged by AC power when a high voltage battery is charged by the AC power.
2. Description of the Related Art
Due to problems such as global warming caused by environmental destruction, high oil prices, and the like, the development of electric vehicles has recently been rapidly progressing in the automobile industry. Currently, major automobile manufactures around the world are conducting research and development to manufacture electric vehicles as their main vehicles.
Electric vehicles emit no exhaust gas and make a very small noise. Electric vehicles were manufactured earlier than gasoline vehicles in 1873. However, due to heavy batteries and long charging time, electric vehicles have not been put to practical use. Meanwhile, as pollution problems have become serious in recent years, electric vehicles are being developed again. However, since the number of times of use of rechargeable batteries is limited, the use of batteries alone cannot ensure a long distance drive.
Therefore, in the current markets, hybrid vehicles using two types of power sources, such as a fossil fuel and a battery, are actively on sale in the North America. Prius manufactured by Toyota Motor Corporation of Japan is a representative hybrid vehicle. Prius includes a gasoline engine, an alternator capable of converting kinetic energy recovered during the braking of a vehicle into electrical energy, and a motor.
Meanwhile, in the case of electric vehicles, methods of using a rechargeable battery (that is, an improvement in the performance of a secondary battery), a fuel cell having different characteristics from an existing cell, and the like, has been provided. Accordingly, the existing problems caused by a battery charging and a frequent replacement cycle in the electric vehicles have been gradually solved.
In the case of some small electric vehicles, not electric vehicles for general road drive, electric vehicles were already commercialized and are now widely used. For example, electric vehicles are widely used for golf carts in golf courses, vehicles for transporting players and equipments in stadiums, indoor drive vehicles, indoor cleaning vehicles, and the like, and it is expected that electric vehicles will be rapidly distributed and applied to commercial vehicles and sedans.
Electric vehicles and hybrid vehicles charges a high voltage battery mounted thereon and uses the high voltage battery as a power source. Vehicles are equipped with a high voltage battery for drive power, and an auxiliary battery for operating an electronic control unit (ECU).
As illustrated in FIG. 1, a conventional battery charging apparatus 1 includes an AC power 11, an on board charger (OBC) 12, an auxiliary battery 13, a high voltage battery 14, and a low voltage DC-DC converter (LDC) 15.
In order to charge the high voltage battery 14, the OBC 12 requires a high voltage charging unit 121 configured to convert the commercial AC power 11 into a high voltage.
However, the conventional battery charging apparatus 1 is designed to charge the high voltage battery 14 alone and consume the auxiliary battery 13 if an ECU using an ignition (IGN) power is operated during the charging.
Therefore, if the voltage of the auxiliary battery 13 is lowered, the battery charging apparatus 1 needs to operate the LDC 15 to charge the auxiliary battery 13. Also, since it is difficult to determine whether the auxiliary battery 13 needs to be charged, an efficient voltage management of the auxiliary battery 13 is difficult.
Moreover, since the LDC 15 charges the auxiliary battery 13 with an auxiliary voltage through a process of converting a high voltage into a low voltage in the high voltage battery 14, the high voltage of the high voltage battery 14 is consumed. Therefore, the number of times of charging/discharging of the high voltage battery 14 is increased, shortening the lifespan of the high voltage battery 14.